Collectively, those fact-checks have formed report cards for each candidate that reveal patterns and trends about their truth-telling. With the Iowa caucuses three days away, PolitiFact is publishing the records to show how the candidates have fared on the Truth-O-Meter. A few findings:

• Rep. Ron Paul has the largest percentage of True statements. They account for 25 percent of the Paul claims we've checked. Romney and Rick Santorum are tied for second with 23 percent.

• Bachmann has the most ratings on the False end of the scale, with 72 percent Mostly False or lower. She is followed by Newt Gingrich with 62 percent and Texas Gov. Rick Perry with 50 percent.

• Bachmann also ranks first for the largest share of Pants on Fire ratings (23 percent). Gingrich is second with 21 percent.

Political analyst Stuart Rothenberg said credibility matters in the campaign, particularly for newcomers such as Bachmann and Perry.

"Because they were not known nationally, they had more to prove and to introduce themselves," he said. "They couldn't afford early mistakes that would define them."

Career statistics

The PolitiFact report cards represent the candidates' career statistics, like the back of their baseball cards. For President Barack Obama, Paul and Romney, they include claims we checked during the 2008 campaign. The totals include statements the candidates made in past or current jobs, such as claims Perry made as Texas governor.

The Truth-O-Meter fact-checks were done by writers for PolitiFact National and our nine state sites. Of the Republicans, Perry has been checked the most (112), followed by Romney (88). Obama has been checked the most of anyone — 331 times — which is nearly as much as all the Republicans combined.

PolitiFact editors choose the claims to check based on whether a statement is significant, verifiable and whether people are likely to wonder if it's true. The tallies are not scientific, but they provide interesting insights into a candidate's overall record for accuracy.

Bachmann's Truth-O-Meter report card became a topic for the New York Times and Minnesota political writers because her first 13 ratings were either False or Pants on Fire. (Her 14th was a Mostly False.)

She has been asked about her PolitiFact record on Meet the Press, Face the Nation and Good Morning America. She usually has sidestepped the questions and used them as an opportunity to criticize President Obama.

Other candidates also have raised questions about her credibility. When Gingrich said at a Dec. 15 debate that she had her facts wrong about his work for Freddie Mac, Bachmann used an unusual tactic to defend herself — she cited PolitiFact's fact-checking from the previous debate, which she said showed "everything I said was true."

But that, too, was incorrect, and she earned another Pants on Fire.

Of the 53 Bachmann claims we've rated, 59 percent earned a False or Pants on Fire, our rating for things that are ridiculously false. By comparison, Gingrich's share of False/Pants on Fire ratings is 44 percent, followed by Santorum with 31.

Leaning toward True

Take a look at the report cards and you can see some patterns.

Paul's record leans toward the True end of the scale. True and Mostly True ratings accounted for half of his Truth-O-Meter ratings. Romney's record is relatively even, with about the same number of True and Mostly True (35) as Mostly False/False/Pants on Fire (34).

Until recently, Gingrich had a relatively even record, with roughly the same number for each rating. But it has fallen lately because of a spate of False and Pants on Fires.

Perry's ratings lean False, with 51 percent of his ratings Mostly False or lower. Jon Huntsman's record is lumped in the middle, with more than three-fourths of the ratings between Mostly True and Mostly False. Santorum's ratings tilt toward the bottom of the scale, with three-fourths Half True or lower.

The 331 checks on Obama also reflect claims made by spokesmen from the White House and his re-election campaign. His record leans toward the True end of the scale, with almost three-fourths of his ratings Half True or higher.

It's probably no coincidence that the Republican candidates with better records — Romney and Paul — have run for president before. They have veteran campaign staffers who have checked their talking points.

But the new candidates haven't fared so well.

A key moment for Bachmann came after a September debate in Tampa when she claimed that the HPV vaccine causes mental retardation. It was debunked by PolitiFact and other fact-checking organizations.

"She hurt herself very badly" with political analysts whose handicapping is influential with GOP supporters and contributors, said David Birdsell, dean of public affairs at Baruch College in New York.

"That was very much a pivot point in the coverage of her campaign," he said.

Birdsell said the impact of the ratings depends on the group. He said Republican primary voters discount the importance of fact-checks on claims they consider in dispute, such as Perry's statement that scientists are questioning whether climate change is man-made (which PolitiFact rated False). But journalists and political analysts put greater importance on those fact-checks.

He said fact-checking "is not going to matter to all audiences all the time — particularly in this environment of contested facts."